This invention relates in general to systems for sensing information at a plurality of remote locations and exchanging the sensed and other information with a central monitor station. More particularly, the invention involves a wireless system in which plural, portable attendants carried by individual operators can monitor their safety, detect the presence of hazardous gases, report the location of the individuals and rapidly provide assistance when needed.
A wide variety of hard-wired systems have been developed for detecting hazardous conditions at spaced locations and reporting the presence of hazards to a central location. Typically, these may be used for detecting the presence of smoke and fire, as in the system described by Tice et al. in U.S. Pat. No. 4,916,432. The condition, e.g. temperature, of refrigerated containers stowed aboard ships and at shipping terminals can be monitored by sensors at the container locations, hard wired to a central location which can sound an alarm if temperatures rise, as described by Vercellotti et al. in U.S. Pat. No. 4,896,277. Where a number of cylinders of hazardous gases are stored in a warehouse, factory or the like, gas detectors may be provided at various locations to detect gas leaks and send an alarm signal through a wire to a central processor in the event of a leak, as described by David et al. in U.S. Pat. No. 4,866,594. Similarly, security systems of the sort described by Skret in U.S. Pat. No. 4,980,913, have a plurality of intrusion detectors wired to a central control station to sound an alarm, notify police, etc., upon detection of an intrusion.
While these systems are effective in fixed locations, such as rooms in a building, they are not portable or adaptable to changing conditions. They are not capable of sensing hazardous conditions involving persons moving from locations to location, such as moving in and out of rooms, tunnels, etc., and generally accomplish a single purpose.
Very specific protective occupational safety and health regulations are in effect governing the entry of persons into confined spaces, areas where hazardous gases may be present and the like. Often, a human attendant must be present outside the space or area, continuously observing the person working in the area. Such attendants are expensive, sometimes are distracted and may not be able to clearly see the working person in narrow spaces, such as curved tunnels. Should the working person be overcome by gases such as carbon monoxide or simply the absence of oxygen, the attendant must summon help, which may take a dangerously long time to arrive.
Thus, there is a continuing need for a portable system for monitoring conditions at remote sites that can sense adverse conditions, warn the user of the danger and sound an alarm at a central location from which help can be immediately dispatched. The system must be portable and compact so that it can be easily carried by workers (or other person operating the system) moving among work sites, e.g. in tunnels, small contiguous compartments and the like. Also needed is a system for determining when a worker is incapacitated or overcome by hazardous conditions. Where the worker is moving about, it is necessary to be able to rapidly determine his position in the event of an emergency.